Wheelchair

ABSTRACT

A system for providing an automated axial force to a continuously variable transmission (CVT) in a wheelchair. An electronic transmission control receives one or more input signals generated by throttle position or other variables. The microprocessor generates an output signal that adjusts the axial force applied to a CVT thereby automatically adjusting the input to output ratio. The invention also provides a manually controlled variator is designed for use on a wheelchair. The manual shifter hydraulically adjusts an axial force imparted on a variator in communication with a wheelchair wheel and a hand rim. Application of the axial force causes the hand rim input and wheelchair wheel output ratio to change, permitting a wheelchair operator to manually adjust the input to output ratio to more easily operate the wheelchair.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/686,303, filed on Mar. 14, 2007, which claims the benefit of andpriority to U.S. Provisional Patent Application No. 60/782,046 filedMar. 14, 2006. Each of the above-referenced applications is herebyincorporated by reference in its entirety.

TECHNICAL FIELD OF INVENTION

The present invention relates generally to a continuously variabletransmission (CVT) and specifically to an improved wheelchair thatincorporates a CVT.

BACKGROUND OF THE INVENTION

A transmission is any mechanical linkage that converts an input torqueto an output torque. It usually involves a series of gears that havediffering diameters, allowing a first gear at a first rotation rate tolink to a second gear rotating at a second rate. The most commonapplication for transmissions is in a vehicle. For example, a car mayhave an automatic transmission or a manual transmission. A bicycle has asimple transmission that links the pedals to the hub of the rear wheel.

Transmissions allow an input force to be converted into a more usefuland appropriate output. However, by using gears and linkages, a typicaltransmission may only have four or five ratios available. For example, afour speed automatic transmission in a car has only four sets of outputgears to couple to the engine's input. A ten speed bike has only tenratios of input to output. A need exists for a transmission that is notlimited by the number of gears. Yet, to place a larger number of gearsinto a transmission increases its costs and weight and spacerequirements.

A continuously variable transmission (CVT) or continuously variableplanetary (CVP) is a transmission that eliminates the need for aspecified number of gears. Instead it allows an almost limitless numberof input to output ratios. This is a benefit because it allows an outputto be achieved, i.e. the speed of a vehicle, at an optimal input, i.e.the rpm of the engine. For example, an engine might be most efficient at1800 rpm. In other words, the peak torque output for the engine might beachieved at this engine rpm, or perhaps the highest fuel economy.Consequently, it may be desirable to run at a specified RPM for aneconomy mode or a power mode. Yet, in third gear, the car might be goingfaster at 1800 rpm than the driver desires. A continuously variabletransmission would allow an intermediate ratio to be achieved thatallowed the optimal input to achieve the desired output.

CVTs have a variator for continuously variable adjustment of the ratio.A customary structure is a belt drive variator having two pairs ofbeveled pulleys and rotating a torque-transmitter element therein, suchas a pushing linked band or a chain. The beveled pulleys are loaded withpressure from the transmission oil pump in order, on one hand, toactuate the ratio adjustment and, on the other, to ensure a contactpressure needed for transmission of the torque upon the belt driveelement. Another usual structure is a swash plate variator insemi-toroidal or fully toroidal design.

Examples of CVTs are exemplified by U.S. Pat. Nos. 6,419,608 and7,011,600 assigned to Fallbrook Technologies of San Diego, Calif. Ineach of those references the axial movement of a rod or an axial forceas indicated by numeral 11 of each reference is used to vary the inputto output ratio of such transmissions. While a continuously variabletransmission is artful on paper, the realities of making one worksmoothly requires significant know how. Consequently, a need exists fora system that permits axial shifting of the rod 11.

While CVTs have primarily been applied to more conventional vehiclessuch as motor scooters and bicycles, wheelchairs represent another classof transport that has been inadequately equipped over the years.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed towards a system forproviding an automated axial force to a CVT. In one embodiment, thesystem comprises an electronic transmission control for a CVT that isadjusted by an axial force provided by a motor. The electronictransmission controls comprises a sensor for receiving an input signalthat is dependent upon one or more automatically-generated variablessuch as throttle position, the current draw from the battery, thevariator setting, the level of charge in the battery or battery level,the control settings of the motor controller (e.g., linear or s-curve),the wind direction, the wind speed, and the tire pressure. Amicroprocessor processes the input signals and transmits an outputsignal to a motor that adjusts an axial force that is applied to avariator. The axial force can be applied by a translational force, or athreaded screw. In another embodiment, the transmission ratio is setusing a push button control.

The present invention also provides an improved wheelchair having amanually controlled CVT. In one embodiment, the manual control comprisesa piston bounded by a first fluid reservoir and second fluid reservoircoupled to a hydraulically actuated piston having a pushing fluidreservoir and a pulling fluid reservoir. Application of downward forceto the piston causes fluid to exit from the second fluid reservoir andcauses fluid to enter the pulling fluid reservoir. Simultaneously, fluidis pulled into the first fluid reservoir and out of the pushing fluidreservoir. Consequently, the hydraulically actuated piston moves in afirst axial direction away from the manually-controlled variator.

Alternatively, application of upward force to the piston causes fluid toexit from the first fluid reservoir and causes fluid to enter thepushing fluid reservoir. Simultaneously, fluid is pulled into the secondfluid reservoir and out of the pulling fluid reservoir. Consequently,the hydraulically actuated piston moves in a second axial directiontowards the transmission.

The invention permits a user to adjust the input to output ratio basedupon conditions including the slope of the navigational path or thespeed of a wheelchair. Hence, this invention provides amanually-controlled variator for a wheelchair that a person can use toeasily adjust the input to output ratio. Consequently, the instantinvention provides an easy way to use a continuously variabletransmission or manually controlled variator on a wheelchair.

In one aspect, the present invention permits one to manually adjust theinput to output ratio applied to two or more wheels and thereby steerthe vehicle.

The above as well as additional features and advantages of the presentinvention will become apparent in the following written detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofan illustrative embodiment when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a schematic representation depicting the operation of manuallycontrolled variator in a light electric vehicle;

FIG. 2 is a schematic representation depicting various potentialembodiments of the present invention in a light electric vehicle;

FIG. 3A is a schematic representation of the automatic operation theoryin accordance with one embodiment of the present invention;

FIG. 3B is a schematic representation of the 90° gearbox in accordancewith one embodiment of the present invention;

FIG. 4A is a schematic representation of a linear actuator in accordancewith an alternative embodiment of the present invention;

FIG. 4B is a schematic representation of a servo motor mounted on a rearwheel in accordance with an alternate embodiment of the presentinvention;

FIG. 4C is a schematic representation of an alternate servo motor designin accordance with another embodiment of the present invention;

FIG. 4D is a simplified schematic representation of a servo motormounted remote from the rear wheel in accordance with an alternativeembodiment of the present invention;

FIG. 5 is a side view illustration of a manually controlled variatormounted on a wheelchair in accordance with one embodiment of the presentinvention;

FIG. 6 is a rear view illustration of the manually-controlled variatorand wheelchair depicted in FIG. 5;

FIG. 7 is a perspective view illustration of the manually-controlledvariator and wheelchair depicted in FIG. 5;

FIG. 8 is a schematic representation of the input rpm and resultantoutput rpm based upon the lever position in accordance with oneembodiment of the present invention;

FIG. 9 is a simplified schematic representation depicting aconfiguration that permits manual steering of a vehicle having two setsof three variators with each set in series in accordance with oneembodiment of the present invention; and

FIG. 10 is a partial simplified schematic representation depicting twovariators in series in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION

FIG. 1 is a schematic representation depicting the operation of manuallycontrolled CVT or variator in a light electric vehicle, such as amotorized wheelchair. As shown in FIG. 1, a manual push button controlbox 101 has buttons corresponding to a signal output 108 of 0% 102, 25%103, 50% 104, 75% 105, and 100% 106 sent to a microprocessor 112. Themicroprocessor output can be shown on a display 150. The microprocessor112 interfaces with a motor control board 114 which receives power froma battery pack 118.

A servo motor 120 engages a 90° gearbox 122 which provides an axialforce 130 to a variator (CVT) 132 in contact with the rear wheel 134. Asused herein, the term “variator” is synonymous with a continuouslyvariable transmission or an infinitely variable transmission, or acontinuously variable planetary, terms known to those skilled in theart. For example, CVTs can include devices where power transfer occursthrough an endless torque-transmitting means that circulates between twopairs of conical disks whereby the effective radius of each conical diskpair is variable by changing the spacing between the disks. Othersteplessly adjustable transmissions can be based upon rolling elementsthat run frictionally engaged between suitable toroidal surfaces.

The rear wheel 134 is powered by a chain 136 or other equivalent meansconnected to a drive motor 140 (e.g., Briggs & Stratton ETEK). The motor140 speed is regulated by a current sent by a motor control device 144.The motor control device 144 is regulated by a throttle 146 and ispowered by a battery 118.

While a user of the electric vehicle can manually shift gears via thepush button control box 101, it is also desirable to have an automaticshifting transmission to permit an electric wheelchair to operate in apower mode or an economy mode.

FIG. 2 is a schematic representation depicting various potentialembodiments of the present invention in a light electric vehicle. FIG.3A is a simplified schematic representation of the automatic operationtheory in accordance with one embodiment of the present invention.Rather than using a push button control box 101 to manually control thetransmission ratio as shown in FIG. 1, one or moreautomatically-generated variables are used to automatically adjust theCVT. For example, referring to FIG. 2 and FIG. 3A, the amount of currentbeing drawn from the motor control device 144 as measured by a currentsensor 242 comprises an automatically generated variable that can beused as an input signal 244 to the microprocessor 112.

Motor controllers such as those available from Altrax of Grants Pass,Oreg. can be used. In one embodiment, the microprocessor 112 comprises abasic stamp board available from Parallax, Inc. of Rocklin, Calif. Themicroprocessor 112 can be programmed to generate a lookup table toprovide optimum set points for variable inputs to obtain either the bestperformance or optimal efficiency of the wheelchair.

Referring to FIG. 2 and FIG. 3A, the wheelchair speed is automaticallygenerated by a sensor 236 mounted on the front wheel 136. In oneembodiment, the sensor 236 comprises a plurality of magnets mountedaround the front wheel rim and a hall effect sensor mounted via abracket and wired to the microprocessor 112. The hall effect sensor 236transmits a pulse of input signal to the microprocessor 112 each time amagnet passes the hall effect sensor 236. Based on the frequency ofpulses or input signals the microprocessor 112 can calculate a speed andan output signal to adjust the axial force provided to the CVT.

Similarly, motor speed may also be calculated by placing another halleffect sensor 232 on the motor 140 which provides an input signal 234 tothe microprocessor 112 each time a magnet passes the hall effect sensor232.

The speed is just one example of an automatically generated variable.Other examples of automatically generated variables include, but are notlimited to the throttle position, the current draw from the battery, thevariator setting, the level of charge in the battery or battery level,the control settings of the motor control device (e.g., linear ors-curve), and tire pressure.

In the example depicted in FIG. 3A, the microprocessor 112 receives datafrom the front wheel speed sensor 236 and current draw sensor 244. Themicroprocessor 112 then outputs a signal to the servo 120, which in turnprovides an axial force to the variator 332 to shift in an optimalmanner that minimizes current draw 244 or power drain so as to provideoptimal efficiency.

FIG. 3B is a schematic representation of the 90° gearbox in accordancewith one embodiment of the present invention. The gearbox 322 comprisesa servo 320 mounted with bolts 310 to the wheelchair frame (not shown).A coupler 323 is disposed between a threaded (worm) shaft 324 and theservo 320. Upon rotation of the threaded shaft 324, the wheel 326rotates as depicted by numeral 328, causing the shift shaft 330 torotate. Such rotation of the shift shaft 330 is converted into an axialforce.

The 90° gearbox setup is used to provide a mechanical advantage (i.e.36:1) and to reduce the size of the protrusion from the side of thewheelchair.

When the system is turned on the servo motor 320 is driven towards homeuntil the shift shaft 330 contacts the home sensor 250 (shown in FIG.2). The servo is stopped and the microprocessor 112 sets the internalelectronic home position, registering voltage, turns, and rotationdirection. In response to button push, based on the last known servoposition a comparison is made between the current position and the“button called” position. The microprocessor 112 then drives the servo320 to the “called” position.

FIG. 4A is a simplified schematic representation of a linear actuator inaccordance with an alternative embodiment of the present invention. Thisembodiment uses a rack and pinion setup and can be mounted close insidethe frame of the wheelchair. The end 416 of the threaded shaft 424 isadapted to couple between a first tooth-like member 412 and a secondtooth-like member 414. As the servo motor rotates the shaft end 416, thefirst tooth-like member 412 is driven axially and thereby provides anaxial force to a member 410 that is in communication with the tooth-likemember 412 and a variator (not shown).

FIG. 4B is a schematic representation of a servo motor mounted on a rearwheel in accordance with an alternate embodiment of the presentinvention. The servo motor 420 is connected to a shaft 430 having athreaded portion 424 adapted to couple with a threaded variator shaft(not shown). The internal threaded portion 424 allows space for thevariator shaft to be pulled in and out. The servo motor 420 turns theshaft 430 thereby causing the threaded portion 424 to move the variatorshaft in or out, thus adjusting the variator.

FIG. 4C is a schematic representation of an alternate servo motor designin accordance with another embodiment of the present invention. Like theembodiment depicted in FIG. 4B, the servo motor 420 in this embodimentis also mounted at the rear wheel of the wheelchair. However, in thisembodiment, the servo motor 420 is connected to a shaft 430 having asplined portion 425 adapted to couple with a variator shaft (not shown).The servo motor 420 turns the splined shaft 430, thereby creating anaxial force on the variator shaft, thus adjusting the variator.

FIG. 4D is a schematic representation of the servo motor incommunication with a hub that contains the variator in accordance withanother alternate embodiment of the present invention. In thisembodiment, a hub 1102 containing the variator is mounted at the rearwheel of the wheelchair (not shown), and the servo motor is mounted upon the wheelchair frame. The rear hub 1102 includes a housing having anaxial force that encloses and protects a pulley system coupled to cables1012 and 1014. These cables 1012, 1014 in turn are connected to theservo motor 420, which alternately pulls cable 1012 or cable 1014 inorder to adjust the variator inside the hub 1102.

While the above description covers examples of how an electronictransmission control can automatically adjust the axial force providedto a variator, the axial force can also be adjusted manually in amotorized or non-motorized vehicle. For example, in accordance with oneembodiment of the present invention, a wheelchair is equipped with amanually activated wheel piston assembly that allows a person with alevel of disability to exert a constant force to an input and achieve anoptimum output to the drive wheels.

FIG. 5 is a side view illustration of a manually-controlled variatormounted on a wheelchair in accordance with one embodiment of the presentinvention. FIG. 6 is a rear view illustration of the manually-controlledvariator and wheelchair depicted in FIG. 5. FIG. 7 is a perspective viewillustration of the manually-controlled variator and wheelchair depictedin FIG. 5.

Referring to FIGS. 5, 6, and 7, in one embodiment themanually-controlled variator comprises a lever 510 having one endpivotally 511 attached 512 to an arm 514 in communication with twopistons 516 a 516 b. Each piston 516 a 516 b is bound by a first fluidreservoir 518 a 518 b and second fluid reservoir 520 a 520 b. The firstfluid reservoir 518 a 518 b is in hydraulic communication with a wheelpiston assembly 550 a 550 b in axial communication with a CVT 100 a 100b.

Pushing forward on the lever 510 forces the arm 514 downward and forceseach piston 516 a 516 b downward. As a result, positive hydraulicpressure is applied to the fluid in the reservoir 520 a 520 b forcingfluid through the flexible hoses 526 a 526 b into a coupler 530 andthrough hard piping 532 a 532 b into a reservoir 552 a 552 b. Thecoupler 530 merely provides a means for switching from a flexible hose522 a 522 b 526 a 526 b into a rigid line 532 a 532 b 536 a 5360. Thisembodiment can be advantageous as it can keep flexible hoses 522 a 522 b526 a 526 b from interfering with or becoming tangled with a user'shands, the wheelchair wheel 570 a 570 b and/or the hand rim 560 a 560 bduring rotation.

When positive hydraulic pressure is applied to the pushing reservoir 552a 552 b, the piston 556 a 556 b forces the arm 558 a 558 b attached tothe piston to move in the direction towards the CVT 100 a 100 b asindicated by arrow 555 a 555 b. Similarly, when positive hydraulicpressure is applied to the pulling reservoir 554 a 554 b, the piston 556a 556 b forces the arm 558 a 558 b attached to the piston to move in thedirection away from the CVT 100 a 100 b as indicated by arrow 551 a 551b.

One advantage of the embodiment described above is the efficient designof the hydraulic system. For example, when the lever 510 is pushedforward the arm causes the piston 516 a 516 b to push fluid out of thesecond fluid reservoir 520 a 520 b to the pulling reservoir 554 a 554 band simultaneously pull fluid into the first fluid reservoir 518 a 518 bfrom the pulling reservoir 552 a 552 b. Consequently, both the firstfluid reservoir and second fluid reservoir are in hydrauliccommunication with the arm 558 a 558 b via the piston 556 a 556 b. Itshould be noted that the above example is provided merely for purposesof illustration. For example, in one embodiment, the second fluidreservoir 520 a 520 b is not in communication with the second piston 556a 556 b.

FIG. 8 is a schematic representation of the Input RPM and resultantOutput RPM based upon the variator position in accordance with oneembodiment of the present invention. Referring to FIGS. 5 and 8 theposition of the lever 510 can move from a position closest to the user(“0” position) to a position furthest from the user (“100” position).The present invention permits an operator to easily change the input tooutput ratio by merely moving the lever 510.

As used herein, an input to output ratio is defined as the number ofhand rim 560 a 560 b revolutions divided by the number of correspondingwheelchair wheel 570 a 570 b revolutions. For example, referring to FIG.8, when the lever is in a position close to zero, one RPM input to thehand rim 560 a 560 b results in a greater RPM output by the wheelchairdrive wheels 570 a 570 b. This is similar to “high gear” in a gearedtransmission and permits an operator better control to slow downhillmovement or rapid level surface movement.

At the intersection of the Input RPM and Output RPM lines, one RPM inputto the hand rim equals one RPM at the wheelchair drive wheels 570 a 570b. Such configuration may be desirable for level surface operation. Inone embodiment, the input to output ratio for level surface operationscomprises between about 1.0 and about 1.8.

When the lever position is in a position close to 100, an input of oneRPM to the hand rims 560 a 560 b will equal less than one RPM of inputto the wheelchair drive wheels 570 a 570 b. Such configuration issimilar to low gear in a geared transmission and permits an operator tomore easily climb inclined surfaces. In one embodiment, the input tooutput ratio for climbing an inclined surface comprises between about0.5 and about 1.0.

FIG. 9 is a simplified schematic representation depicting aconfiguration that permits manual steering of a vehicle having two setsof three variators with each set in series in accordance with oneembodiment of the present invention. As shown in FIG. 9, each variator900 a 900 b 900 c 900 d 900 e 900 f has a corresponding wheel pistonassembly 950 a 950 b 950 c 950 d 950 e 950 f. The wheel pistonassemblies are similar in operation to the assembly depicted in FIG. 7.

In this embodiment, steering is achieved by changing the input to outputratio to a first set of variators 900 a 900 b 900 c in communicationwith drive wheels 970 a 970 b 970 c on a first side of a vehiclerelative to a second set of variators 900 d 900 e 900 f in communicationwith wheels 970 d 970 e 970 f on a second side of a vehicle. Forexample, pushing forward on the first lever 910 a forces the piston 916a downward. As a result, positive hydraulic pressure is applied to thefluid in the reservoir 920 a forcing fluid through the flexible hose 926a into a coupler 930 a and through hard piping 932 a into a reservoir952 a. When positive hydraulic pressure is applied to the pushingreservoir 952 a, the piston 956 a forces the arm 958 a attached to thepiston to move in the direction towards the variator 100 as indicated byarrow 955 a.

Similarly, by pulling back on the first lever 910 a positive hydraulicpressure is applied to the first fluid reservoir 918 a through theflexible hose 922 a and through the hard piping 936 a to the pullingreservoir 954 a. Consequently, the piston 956 a forces the arm 958 aattached to the piston to move in the direction away from the CVT 900 aas indicated by arrow 951 a.

In one embodiment, one or more of the variators 900 a 900 b 900 c 900 d900 e 900 f comprise an infinitely variable transmission (IVT).Consequently, adjusting the axial direction applied to the first set ofvariators 900 a 900 b 900 c can turn the first set of wheels 970 a 970 b970 c in a direction different from the second set of wheels 970 d 970 e970 f. As a result, the vehicle can have a little or no turning radius.Further, such embodiment can be used to manually put the vehicle inreverse.

As previously discussed, a variator is designed to vary an input tooutput ratio in the same way as gears change the input to output ratioon a car or bicycle. The input to output ratio is changed based upon theaxial movement of a rod connected to the variator. The axial movementcan be provided by a manual hydraulic system as exemplified by FIG. 7,by a manual electric system as exemplified by FIG. 1, or by a manualmechanical system as described by co-pending application U.S. Ser. No.11/409,846. Furthermore, the axial movement, and hence input-to-outputratio, can also be adjusted automatically based upon an automaticallygenerated input signal. The axial adjustment can occur throughhydraulic, electrical, or mechanical means.

The present invention also contemplates the combination of the variousways of changing the input to output ratio. One example of the way inwhich the variators can be combined is depicted in FIG. 10, which is apartial simplified schematic representation depicting two variators inseries in accordance with one embodiment of the present invention.

As shown in FIG. 10, an input RPM is provided by a rotating member 1140attached to a motor (not shown). The rotating member 1140 can createsrotation in input shaft 1132 a connected to a first variator 1000 a by achain, cable 1135 a or other endless torque-transmitting means. Thefirst variator output shaft is connected to a rotating member 1034 aconnected to a second variator 1000 b input shaft 1132 b.

The first variator input-to-output ratio can be adjusted by axialmovement of a rod 1110 a that can be adjusted by hydraulic, electrical,or mechanical device. The second variator 1000 b output shaft isconnected to a wheel 1070. Consequently, a wider range ofinput-to-output ratios can be achieved by having two or more variatorsin series. For example, if the first variator is capable of achieving aninput to output ratio of 1:10 and the second variator is capable ofachieving an input to output ratio of 1:10, an overall input to outputratio of 1:100 can be achieved. Furthermore, a wider range of controlcan be achieved. For example, in one embodiment, a second device foradjusting a second axial force 1000 b to a second continuously variabletransmission or variator 1000 b is based upon an automatically generatedoutput signal such as vehicle speed. Such embodiment can be beneficialto provide an overdrive or ultra-low gear for climbing a hill.

The description of the present invention has been presented for purposesof illustration and description, and is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theembodiment was chosen and described in order to best explain theprinciples of the invention, the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A light electric vehicle comprising: a first wheel; a drive motorconfigured to drive the first wheel; a continuously variabletransmission (CVT) disposed between the first wheel and the drive motor,the CVT having a variator shaft, wherein the variator shaft isconfigured to axially translate and thereby adjust an input to outputratio between the drive motor and the first wheel; a splined shaftoperably coupled to the variator shaft; an electric servo motor coupledto the splined shaft, the servo motor configured to rotate the splinedshaft and thereby axially translate the variator shaft to provide anaxial force to the CVT, wherein the axial force is configured tomanipulate the CVT between at least a first position and a secondposition, and wherein the input to output ratio between the drive motorand the first wheel is different when the CVT is in the first positionthan when the CVT is in the second position; and a battery, wherein thedrive motor and the servo motor are configured to draw power from thebattery.
 2. The light electric vehicle of claim 1, further comprising amicroprocessor configured to provide a control signal to the servo motorto control the axial force provided to the CVT.
 3. The light electricvehicle of claim 2, further comprising a first sensor configured tosense a characteristic of the drive motor and to provide a first signalto the microprocessor, wherein the first signal is a function of thecharacteristic of the drive motor.
 4. The light electric vehicle ofclaim 3, wherein the first sensor comprises a current draw sensorconfigured to sense the current drawn from the battery by the drivemotor.
 5. The light electric vehicle of claim 3, wherein the firstsensor comprises a speed sensor configured to sense a speed of the drivemotor.
 6. The light electric vehicle of claim 3, further comprising: asecond wheel; and a second sensor configured to sense a speed of thesecond wheel and to provide a second signal to the microprocessor,wherein the second signal is a function of the speed of the secondwheel.
 7. The light electric vehicle of claim 6, wherein the controlsignal is a function of at least the first signal and the second signal.8. The light electric vehicle of claim 1, further comprising a gearboxdisposed between the servo motor and the CVT.
 9. The light electricvehicle of claim 1, wherein the light electric vehicle comprises awheelchair.
 10. The light electric vehicle of claim 1, furthercomprising a control board, wherein the control board is disposedbetween the servo motor and the microprocessor, and wherein the controlboard is disposed between the servo motor and the battery.